The present invention refers to the main component parts of an injection mold adapted to enable a plastic substance in its fluid, i.e. molten state, usually just after the extrusion thereof, to be injected into appropriate cavities for forming related preforms. In particular, the present invention applies, in a preferred manner, to machines adapted for molding a plurality of plastic articles at the same time, ie. the so-called xe2x80x9cpreformsxe2x80x9d that are intended for subsequent processing by blow molding into appropriate final containers, especially plastic bottles.
Although reference will be made in the following description, mainly for reasons of greater descriptive convenience, to a machine for moulding preforms of plastic material, as this is used in combination with the preliminary steps of melting and extrusion of said plastic material, it will be appreciated that the present invention shall be understood as applying also to other kinds of uses or applications, as far as these fall within the scope of the appended claims.
It is generally known in the art that, during the preform molding operation, use is generally made of a molding machine comprising a stationary half-mold, which is firmly joined to the structure of the same machine, and a moving half-mold, which preferably moves in a vertical direction and is selectively closable into an appropriate position against the stationary half-mold.
In prior-art solutions, the stationary half-mold usually comprises a base plate 1, a nozzle-carrying plate 2, a cavity-carrying plate 3, at least a hot runner 4, a plurality of nozzles 5, a plurality of resistive elements 6 associated with the hot runner, and a plurality of resistive elements 7 associated with the nozzles 5.
The nozzle-carrying plate 2 is in the shape of a U turned upside down, and is arranged in an intermediate position between the base plate and the cavity-carrying plate. This is illustrated in FIGS. 1 and 2, which are views of the three different plates in assembled and separated positions thereof, respectively.
The resistive elements 6 are connected to a power supply source (not shown) via a respective plurality of electric conductor leads 9. Each one of them is furthermore inserted in a wall of the nozzle-carrying plate and passes therethrough, coming out on the outside thereof, where it is connected to a respective terminal clamp of an appropriate connector 14.
The resistive elements 7 that are associated with the nozzles 5 in the nozzle-carrying plate 2 are in turn connected to a power supply source (not shown) via a respective plurality of electric conductor leads 11, connecting the respective resistive element 7 to a respective terminal clamp comprised in the same connector 14 that already connects the above-described electric conductor leads 9.
It is therefore obvious that each one of the electric conductor lead 11 is contained, as shown in the Figures, in the body of the nozzle-carrying plate 2.
All this is anyway largely known to ail those skilled in the art and is only reviewed here shortly in order to more effectively introduce the technical context which the present invention actually refers to.
During the practical use of the mold, there are quite frequently occurring such operating conditions as to make it necessary for access to be gained most conveniently and easily, as well as with a maximum extent of freedom in intervening, to the hot runner or the nozzles. In the majority of the cases, these operating conditions are brought about by the maintenance needs of the hot runner, e.g. due to a failed heating element requiring replacement, or due to a nozzle having plugged up, or, more simply, due to the hot runner itself needing to be cleaned up and cleared of slag and scum depositing therein after a prolonged use.
In all those circumstances in which the nozzle-carrying plate 2 must be disassembled and separated from the hot runner, the need logically arises for all conductor leads 9 to be first disconnected from respective terminal clamps (not shown) in order to be able to disengage the nozzle-carrying plate 2 from the hot runner and then remove the plate 2. However, the disconnection of all the terminal clamps involved in such an operation is considerably time consuming, i.e. requires a lot of time during which the whole plant must of course be kept at a standstill, ie. inoperative.
Upon conclusion of the planned maintenance or similar intervention, the reverse operation must be then carried out to re-connect all the conductor leads to respective terminal clamps. This obviously requires a further lot of time and, therefore, this puts a further downtime penalty on the whole plant.
In other words, such operations of disconnecting and reconnecting the above cited conductor leads, which are inherently rather long and delicate to carry out, demand a considerable extension of the machine downtime and an equally considerable increase in the number of man-hours spent with respect to the time and man-hour requirements of the actual maintenance intervention. Such an extension is hardly compatible with the productivity requirements placed on such machines, which are designed and made for heavy-duty operation, i.e. so as to be able to operate in a substantially continuous manner.
Based on the above considerations, it is therefore a main purpose of the present invention to provide a type of stationary half-mold which is adapted to do away with the above described drawbacks, is capable of being easily implemented using readily available and, therefore, cost-effective materials and techniques, and is further easy, reliable and safe to use.
Such an aim of the present invention, along with further features thereof, is reached in a type of mold that is made and operates as recited in the appended claims.